SOME EFFECTS OF BLADE CHARACTERISTICS ON COMPRESSOR NOISE LEVEL
BOEING COMMERCIAL AIRPLANE CO RENTON WA
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Sound power level and airflow measurements were obtained for flat, cambered, and airfoil blades, with and without twist. A single-stage axial flow compressor or fan of low pressure ratio was used, the simplified design being dictated by the variety of blade shapes tested. Data are given for the dependence of sound power level on flow coefficient, air weight flow, relative tip velocity, and rotational speed. The sound power per unit weight flow appears to be independent of blade shape. The discrete-frequency noise from a freely running rotor is predicted to an order of magnitude in agreement with experimental results by an equation that is intuitively derived from an extension of propeller theory.